I feel really insecure about doing anything sexual.

My boyfriend and I of two years are in a happy, healthy relationship. We waited to have sex until over a year and a half (we were both virgins). He's really good at everything he does, as he did have more experience in other things. He's the only guy I've ever done anything with and I'm not good with anything I do. He's admitted it, that I just need more experience. But it makes me feel terrible because even though he's great with it and never complains, I feel worthless with this. We have such a great relationship and healthy sex life as well, but this is the one thing I'm very insecure about. What could I try to be better with this?